Sparse Swap is a vSAN feature worth highlighting for its space efficiency, and it is available for both all-flash and hybrid environments. By default, vSAN swap files are thick provisioned—created with 100 percent space reservation. (For example, if the VM has 4GB of RAM, then the swap file also has 4GB of RAM.) While this guarantees sufficient capacity for the VM, it can consume too much memory—especially in large clusters with a lot of virtual machines. When Sparse Swap is enabled as an advanced host setting, the VM reserves less than 100 percent of memory space for the swap objects.
Sparse Swap is established by enabling the Swap thick provision disabled setting. Sparse swap files have an FTT setting of 1 and a FTM setting of RAID1 (Mirroring).
Leveraging Sparse Swap is an effective way to reduce memory overhead in environments that are not already over-committing memory, especially for all-flash VxRail environments where swap files represent a sizeable portion of the total required datastore capacity.